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[Linux-cluster] Questions related to cluster quorum and fencing



Hi all,

Quorum -
The questions are bit theoretical, I have gone through documentation and man pages and have understood that, a cluster is "quorate" if a cluster or its partition has nodes, with votes equal to or more than "expected_votes" in "cman" section of cluster.conf file (with no requirement mandating use of quorum disk)

So how does cluster being quorate or non-quorate affects functioning of a cluster or services? If cluster is non-quorate, does it indicate an alarming situation and why?

If a cluster is composed of resource groups which including only IP resource and script resource monitoring my application server listening on IP resource(no shared disk or shared resource between cluster nodes), then is cluster being "quorate" (or non quorate) important for services and/or cluster?

Fencing -
Is fencing and cluster being quorate or non-quorate related? I tried one experiment, wherein I removed "fencing" for cluster nodes and shutdown one of the nodes in cluster. And I got message in /var/log/messages indicating fencing failed for node, and service was not failed over from that node. So is fencing mandatory even if there is no "shared" disk between two cluster nodes?

Also is a cluster non-quorate in a time window when a node has failed and has not been fenced successfully?

Yours gratefully



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